Sounds like it's my fault, actually. I assumed you'd know Irfan View was, more than anything, an image viewer, hence it needs an image to operate. The picture posted was quite self-explanatory, anyhow!
The tutorial:
1. Run your emulator at a display resolution which doubles the resolution of the emulated game. For instance, a SFC game will be generally 256 x 224. You must turn it into 512 x 448. Of course, that's only possible in a windowed (non full-screen) mode. A full-screen mode which DOESN'T stretch the picture (at least, vertically) would also work (notice the actual resolution mode used by your video-card here is of 640 x 480, and some lines will be blank lines). You also must enable 50% scanlines (only a few emulators don't have this option, so for those cases, ask me later, if you happen to find them).
2. Load the game and exit the emulator.
3. Open Irfan View (that means "open an image file with Irfan View") and press "C". This opens the capture setup window. Make your chose. You can even select an automatic capturing mode.
4. Don't close Irfan View and go back to your emulator. Play the game and take the snapshots as you selected.
5. Open one of the snapshots in your HD with Irfan View. Make sure the snapshot is border-free. Go to the Adobe 8BF filters menu and select "Television". You only need to add curvature. Something between 4~8 will serve. Notice you could also add "scanlines" from there, and even some other CRT effects. OK and Exit.
6. Resize the image's width via the Image menu in order to get a 4 : 3 aspect ratio (or whichever suits better for the page layout). Do it with a "resample" method like Lanczos Filter.
7. Let's add some blur now. Go to Image, Effects, Blur.
8. Time to Enhance Colors also from the Image menu. Modify the color balance, contrast and saturation as you prefer. This is a very important phase in the process, so be careful. Its point is to reintegrate the picture its original colors, given that both, the scanlines and the blur darkened it a lot.
9. Add some more blur if necessary, save your changes and there you have it.
